1. Field of the Invention
The present invention relates to P2O5-containing optical glass that is suited to precision press molding, a precision press molding preform comprised of this glass, a method for manufacturing the same, an optical element comprised of this glass, and a method for manufacturing the same.
2. Discussion of the Background
Low-dispersion glass is useful optical glass that is employed as a material in various optical elements. For example, Japanese Unexamined Patent Publication (KOKAI) Showa No. 60-171244 discloses phosphate glass exhibiting low dispersibility with an Abbé number, νd (nud), of about 60 to 73.
The aforementioned phosphate glass is appealing due to its low dispersion, and lenses made from it have a great deal of potential.
However, lenses made from this glass present a problem in that their surface properties deteriorate when cleaned. Examples of deterioration of surface properties are scratches and clouding of the lens surface caused by cleaning, both of which greatly compromise the performance of the lens as an optical element. Further, when an antireflective film is applied, the film adheres poorly, separating over time.
The present invention was devised to solve the above problems and it is an object of the present invention to provide optical glass having an excellent durability for cleaning and yielding a low-dispersion optical element, this optical element, a method for manufacturing the optical element, a glass preform for manufacturing the optical element, and a method for manufacturing the glass preform.